More Like this

1. Search for $$B_{(s)}^{*0}\rightarrow \mu ^+\mu ^-$$ in $$B_c^+\rightarrow \pi ^+\mu ^+\mu ^-$$ decays

   https://doi.org/10.1140/epjc/s10052-024-13573-0  

   Aaij, R; Abdelmotteleb, A_S W; Beteta, C Abellan; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (January 2025, The European Physical Journal C)

   Abstract A search for the very rare$$B^{*0}\rightarrow \mu ^+\mu ^-$$ $B_{}^{\ast 0}\to {\mu }^{+}{\mu }^{-}$and$$B_{s}^{*0}\rightarrow \mu ^+\mu ^-$$ $B_s^{\ast 0}\to {\mu }^{+}{\mu }^{-}$decays is conducted by analysing the$$B_c^+\rightarrow \pi ^+\mu ^+\mu ^-$$ $B_c^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$process. The analysis uses proton-proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9$$\text {\,fb}^{-1}$$ ${\text{,fb}}^{-1}$. The signal signatures correspond to simultaneous peaks in the$$\mu ^+\mu ^-$$ ${\mu }^{+}{\mu }^{-}$and$$\pi ^+\mu ^+\mu ^-$$ ${\pi }^{+}{\mu }^{+}{\mu }^{-}$invariant masses. No evidence for an excess of events over background is observed for either signal decay mode. Upper limits at the$$90\%$$ $90\%$confidence level are set on the branching fractions relative to that for$$B_c^+\rightarrow J\hspace{-1.66656pt}/\hspace{-1.111pt}\psi \pi ^+$$ $B_c^{+}\to J/\psi {\pi }^{+}$decays,$$\begin{aligned} \mathcal{R}_{B^{*0}(\mu ^+\mu ^-)\pi ^+/J\hspace{-1.66656pt}/\hspace{-1.111pt}\psi \pi ^+}&< 3.8\times 10^{-5}\ \text { and }\\ \mathcal{R}_{B_{s}^{*0}(\mu ^+\mu ^-)\pi ^+/J\hspace{-1.66656pt}/\hspace{-1.111pt}\psi \pi ^+}&< 5.0\times 10^{-5}. \end{aligned}$$ $\begin{array}{cc}R_{B_{}^{\ast 0}\left({\mu }^{+}{\mu }^{-}\right){\pi }^{+}/J/\psi {\pi }^{+}}^{}& <3.8\times {10}^{-5}\text{and}\\ R_{B_s^{\ast 0}\left({\mu }^{+}{\mu }^{-}\right){\pi }^{+}/J/\psi {\pi }^{+}}^{}& <5.0\times {10}^{-5}.\end{array}$ 

   more » « less
2. Effective theory tower for μ → e conversion

   https://doi.org/10.1007/JHEP11(2024)076  

   Haxton, Wick; McElvain, Kenneth; Menzo, Tony; Rule, Evan; Zupan, Jure (November 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We present theoretical predictions forμ→econversion rates using a tower of effective field theories connecting the UV to nuclear physics scales. The interactions in nuclei are described using a recently developed nonrelativistic effective theory (NRET) that organizes contributions according to bound nucleon and muon velocities,$$ {\overrightarrow{v}}_N $$ ${\overrightarrow{v}}_N$and$$ {\overrightarrow{v}}_{\mu } $$ ${\overrightarrow{v}}_{\mu }$, with$$ \left|{\overrightarrow{v}}_N\right| $$ $\left({\overrightarrow{v}}_N\right)$>$$ \left|{\overrightarrow{v}}_{\mu}\right| $$ $\left({\overrightarrow{v}}_{\mu }\right)$. To facilitate the top-down matching, we enlarge the set of Lorentz covariant nucleon-level interactions mapped onto the NRET operators to include those mediated by tensor interactions, in addition to the scalar and vector interactions already considered previously, and then match NRET nonperturbatively onto the Weak Effective Theory (WET). At the scaleμ≈ 2 GeV WET is formulated in terms ofu,d,squarks, gluons and photons as the light degrees of freedom, along with the flavor-violating leptonic current. We retain contributions from WET operators up to dimension 7, which requires the full set of 26 NRET operators. The results are encoded in the open-source Python- and Mathematica-based software suite MuonBridge, which we make available to the theoretical and experimental communities interested inμ→econversion. 

   more » « less
3. The immersion poset on partitions

   https://doi.org/10.1007/s10801-025-01380-z  

   Johnston, Lisa; Kenepp, David; Nguyen, Evuilynn; Paul, Digjoy; Schilling, Anne; Simone, Mary_Claire; Zhou, Regina (February 2025, Journal of Algebraic Combinatorics)

   Abstract We introduce the immersion poset$$({\mathcal {P}}(n), \leqslant _I)$$ $(P\left(n\right),{⩽}_I)$on partitions, defined by$$\lambda \leqslant _I \mu $$ $\lambda {⩽}_I\mu$if and only if$$s_\mu (x_1, \ldots , x_N) - s_\lambda (x_1, \ldots , x_N)$$ $s_{\mu }(x_1,\dots ,x_N)-s_{\lambda }(x_1,\dots ,x_N)$is monomial-positive. Relations in the immersion poset determine when irreducible polynomial representations of$$GL_N({\mathbb {C}})$$ $G{L}_N\left(C\right)$form an immersion pair, as defined by Prasad and Raghunathan [7]. We develop injections$$\textsf{SSYT}(\lambda , \nu ) \hookrightarrow \textsf{SSYT}(\mu , \nu )$$ $\mathrm{SSYT}(\lambda ,\nu )\hookrightarrow \mathrm{SSYT}(\mu ,\nu )$on semistandard Young tableaux given constraints on the shape of$$\lambda $$ $\lambda$, and present results on immersion relations among hook and two column partitions. The standard immersion poset$$({\mathcal {P}}(n), \leqslant _{std})$$ $(P\left(n\right),{⩽}_{\mathrm{std}})$is a refinement of the immersion poset, defined by$$\lambda \leqslant _{std} \mu $$ $\lambda {⩽}_{\mathrm{std}}\mu$if and only if$$\lambda \leqslant _D \mu $$ $\lambda {⩽}_D\mu$in dominance order and$$f^\lambda \leqslant f^\mu $$ $f^{\lambda }⩽f^{\mu }$, where$$f^\nu $$ $f^{\nu }$is the number of standard Young tableaux of shape$$\nu $$ $\nu$. We classify maximal elements of certain shapes in the standard immersion poset using the hook length formula. Finally, we prove Schur-positivity of power sum symmetric functions on conjectured lower intervals in the immersion poset, addressing questions posed by Sundaram [12]. 

   more » « less
4. Test of light-lepton universality in τ decays with the Belle II experiment

   https://doi.org/10.1007/JHEP08(2024)205  

   Adachi, I; Adamczyk, K; Aggarwal, L; Aihara, H; Akopov, N; Aloisio, A; Anh_Ky, N; Asner, D M; Atmacan, H; Aushev, V; et al (August 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> We present a measurement of the ratio$$ {R}_{\mu }=\mathcal{B}\left({\tau}^{-}\to {\mu}^{-}{\overline{\nu}}_{\mu }{\nu}_{\tau}\right)/\mathcal{B}\left({\tau}^{-}\to {e}^{-}{\overline{\nu}}_e{\nu}_{\tau}\right) $$ $R_{\mu }=B\left({\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }\right)/B\left({\tau }^{-}\to e^{-}{\overline{\nu }}_e{\nu }_{\tau }\right)$of branching fractions$$ \mathcal{B} $$ $B$of theτlepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKBe⁺e⁻collider. The sample has an integrated luminosity of 362 ± 2 fb⁻¹at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result,R_μ= 0.9675 ± 0.0007 ± 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to theWboson inτdecays of 0.9974 ± 0.0019, in agreement with the standard model expectation of unity. 

   more » « less
5. Measurement of the Higgs boson production via vector boson fusion and its decay into bottom quarks in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP01(2024)173  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Escalante_Del_Valle, A; Hussain, P S; et al (January 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> A measurement of the Higgs boson (H) production via vector boson fusion (VBF) and its decay into a bottom quark-antiquark pair ($$ \textrm{b}\overline{\textrm{b}} $$ $b\overline{b}$) is presented using proton-proton collision data recorded by the CMS experiment at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV and corresponding to an integrated luminosity of 90.8 fb⁻¹. Treating the gluon-gluon fusion process as a background and constraining its rate to the value expected in the standard model (SM) within uncertainties, the signal strength of the VBF process, defined as the ratio of the observed signal rate to that predicted by the SM, is measured to be$$ {\mu}_{\textrm{Hb}\overline{\textrm{b}}}^{\textrm{qqh}}={1.01}_{-0.46}^{+0.55} $$ ${\mu }_{\mathrm{Hb}\overline{b}}^{\mathrm{qqh}}={1.01}_{-0.46}^{+0.55}$. The VBF signal is observed with a significance of 2.4 standard deviations relative to the background prediction, while the expected significance is 2.7 standard deviations. Considering inclusive Higgs boson production and decay into bottom quarks, the signal strength is measured to be$$ {\mu}_{\textrm{Hb}\overline{\textrm{b}}}^{\textrm{incl}.}={0.99}_{-0.41}^{+0.48} $$ ${\mu }_{\mathrm{Hb}\overline{b}}^{\text{incl}.}={0.99}_{-0.41}^{+0.48}$, corresponding to an observed (expected) significance of 2.6 (2.9) standard deviations. 

   more » « less